NASA’s Orion – Going Backwards to Propel the US to the Moon and Beyond

A recent news report stated that Alliant was going to use the funds to build a first stage solid fuel powered engine for the Orion. According to the same experts that served on the board of investigation into the Challenger disaster, and most scientists around the planet, running a solid engine is fraught with issues.
Solid rocket motors are just like a firecracker or skyrocket, once turned on – they cannot be turned off until all their fuel is exhausted. Just like during the Challenger disaster, NASA learned this, so why would they go to a solid fuel solution for Orion, knowing that something similar may happen again?

Liquid fuelled systems tend to be more explosively volatile, as shown in the Nedelin Disaster on October 24, 1960. A Soviet liquid fuelled rocket malfunctioned on the launch pad and ignited it’s second stage motors, burning into the fully fueled first stage, resulting in a catastrophic explosion that killed as many as 120 people.

Liquid fuelled systems can be throttled or turned off if a problem occurs. Cutting power to the fuel pumps will, within seconds, shut off combustion as the fuel and oxidizer stop flowing into the engine bell. A solid rocket can not be turned off until it’s fuel is fully expended.

From an engineering standpoint – liquid fuel is both more efficient in a lot of ways as well as being a great deal more controllable for spacecraft launches.

The main benefit to solid rocket engines has been for long term storage in regards to missiles and explosive projectiles, as well as small satellite launches and final orbital insertion stages for satellite payloads.

Solid engines have a specific impulse(SI) of around 285 seconds, compared to over 330 for Liquid kerosene, and over 450 for Liquid Oxygen/Liquid Hydrogen engines.

The specific impulse(SI) means the amount of change that one unit of propellant can produce in this form of engine. A solid rocket can cause up to 2,500 meters per second change, which the Space Shuttle main engines, with an SI of over 450, can generate up to 4,500 meters per second change. This is a massive oversimplification of a complex chemical reaction formula, but will work for the purposes of this article.

It simply boggles the mind that NASA would rely upon a solid rocket technology, again, to launch it’s people into orbit. This is when every other nation in the world is relying on more powerful and in almost every case, more efficient liquid fuelled engines and launch systems to ensure the most precious cargo is sent to it’s destination properly.